Glomerulonephritis or glomerular nephritis (“GN”) is a renal disease which is characterized by inflammation of the glomeruli or capillary loops of the kidney. It is a pathologic process associated with a number of diverse underlying diseases. The condition occurs in acute, sub-acute and chronic forms and also secondary to an infection. The former conditions, where a concurrent illness cannot be found, are generally referred to as idiopathic glomerulonephritis. The latter conditions are generally referred to as secondary glomerulonephritis. Whatever the underlying cause, immune complexes form and result in a series of events leading to glomerular injury and loss of renal function, proteinuria and ultimately, in some cases, renal failure.
Nephritis is an inflammation of the kidney, which may be a focal or diffuse proliferative or destructive disease involving the glomerulus, renal tubule or the kidney interstitial (or connective) tissue. The most common form of nephritis is glomerulonephritis. Nephritis may progress through a number of stages ending in end-stage kidney disease or end-stage renal failure.
Renal failure results from the inability of the kidney to maintain its normal functions. As a result, metabolic waste products and metabolites accumulate in the blood. These waste products and metabolites may adversely affect most bodily systems. Disturbances in the maintenance of fluid and electrolyte balances are characteristics of renal failure.
Acute renal failure may occur suddenly due to trauma, infection, inflammation or exposure to nephrotoxic substances. This condition may result in dehydration, hypotension and circulatory collapse. Acute renal failure is frequently segregated into three categories: (1) pre-renal failure, which is associated with decreased renal blood flow; (2) intra-renal failure, which is associated with ischemia and toxins; and (3) post-renal failure, which results from obstruction of urine flow.
Chronic renal failure involves a progressive loss of kidney function that may eventually progress to end-stage renal disease or failure. At inception, chronic renal failure begins as a diminishing kidney function, without appreciable accumulation of metabolic waste products in the blood. As the glomerular filtration rate slows due to inflammation, waste products begin to accumulate. The disease progresses to uremia due to low kidney function, and high levels of protein end products start to accumulate and impair bodily functions. Common causes of chronic renal failure include: inflammation, infection, urinary tract obstruction and certain systemic diseases and toxicities, including hypercalcemia, lupus erythematosus, diabetes mellitus and hypertension.
End-stage renal disease is marked by irreversible chronic renal failure. Serum creatinine and blood urea nitrogen levels continue to rise and the resulting uremia impairs all bodily systems. The kidney can suffer permanent and almost complete loss of function on the order of 10% or less of normal kidney function. One cause of end-stage kidney disease is glomerulonephritis. Other causes include those mentioned for chronic renal failure.
Creatinine is a nitrogenous compound formed as a result of creatine metabolism. Creatine, in turn, is a non-proteinaceous substance that is synthesized in the body from three amino acids, arginine, glycine and methionine. The molecule is found in muscle in small amounts and, when combined with phosphate as phosphocreatine, serves as a storage form of high energy phosphate used in various metabolic processes. Creatinine is absorbed into the blood and ultimately is excreted in the urine. Thus, a simple laboratory test for measuring creatinine in the blood can be used to determine kidney function. The test is frequently referred to as a creatinine clearance test, which measures the amount of creatinine cleared from plasma in a given time interval. Because creatinine is formed from phosphocreatine in relatively constant amounts, a rise in creatinine levels in the blood is indicative of a kidney malfunction, i.e., loss of kidney function.
Glomerulonephritis may arise as a result of a biological insult to the immune system. Foreign substances may adhere to the basement membrane and cause an immune response resulting in the production of antibodies. These antibodies may combine with the foreign substances to cause immune complexes that become deposited on the walls of the tiny glomerular capillaries, resulting in damage to the nephron. Alternatively, in some individuals the immune system can create autoantibodies which are immunoglobulins that may attack kidney cells resulting in a so-called autoimmune response. If proteins in the body are altered, an autoantibody response may ensue because the autoantibodies recognize the altered proteins as non-self. These autoantibody-protein complexes may likewise be deposited on the basement membrane of the glomerulus causing a disruption of the functioning of the nephron.
Glomerulonephritis is a common cause of proteinuria in dogs and may be either the idiopathic or secondary form of the condition. In the latter situation, the condition may develop secondary to neoplasia, inflammatory diseases, endocrine malfunctions, infections or familial nephropathies. As in humans, glomerulonephritis in dogs is mediated immunologically, involving immunoglobulins and complement factors in the body of the animal. Injury occurs within the glomeruli of the kidney resulting in morphological changes to the glomeruli. Eventually the injury is irreversible and leads to malfunction of the nephrons.
Glomerulonephritis is characterized in the scientific literature in a number of different forms based on the histopathological changes taking place. Membranous glomerulonephritis involves thickening of the glomerular basement membrane. Proliferative or mesangioproliferative glomerulonephritis is characterized by proliferation of cells in the mesangial matrix. Membranoproliferative glomerulonephritis involves a combination of the foregoing changes. Glomerulosclerosis is characterized by increased matrix formation and scarring. In some cases there are minimal changes to the glomeruli and only slight increases in mesangial cell proliferation.
Diet plays an important role in disease causation and progression because it is fundamentally involved in metabolism. Biological pathways are at some level regulated by nutritional factors. Thus, dietary components present in foods as nutrients may regulate gene expression at the transcriptional and translational level, as well as in certain post-translational modifications. They may similarly be involved in degradation and enzymatic activities. Nutrient levels may influence the equilibrium of metabolic pathways. Metabolic pathways are frequently complex and may involve many redundancies and interrelationships among different metabolic pathways. Altering the concentration of a single enzyme, growth factor, cytokine or metabolite may impact a number of metabolic pathways involved in disease-related physiology. Hormones and other cell signaling molecules are well-understood to be regulated by diet and are also known to be implicated in the development and progression of disease.
The same disease phenotype may result from disturbances in different metabolic pathways, and the genetic make-up of each animal differs, thereby causing variation in responses to the same factors, including nutritional and environmental factors. The interplay of genetic, nutritional and environmental factors is important in understanding the etiology, prevention, treatment and progression of diseases in animals. Finding gene expression responses to nutrients associated with various diseases and disorders permits formulation of diets for animals susceptible to disease such as kidney disorders, and further permits diagnosis, treatment and monitoring the prognosis of the underlying disease or disorder.
As a result, the use of biomarkers for early detection and monitoring of disease progression may enable prevention or treatment of diseases as well as new therapies to be developed for animals, particularly for companion animals. Diet is arguably the most important environmental factor affecting the phenotype of an animal, including susceptibility to disease.
The invention encompasses edible food compositions for companion animals, which have therapeutic and prophylactic efficacy and possess increased palatability over currently marketed companion food products.